JPS62268186A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain excellent luminous characteristics by making the thickness of a fourth semiconductor layer in a section corresponding to a current injection region thicker than that of other fourth layers, forming a distribution of refractive index and confining light to a striped shape. CONSTITUTION:N-Al0.45Ga0.55As 102 is shaped onto substrate P-GaAs 101, and a guide layer 103 and N-Al0.31Ga0.69As 108 are formed and an active layer 104 is shaped onto 108. P-Al0.45Ga0.55As 105 and N-GaAs 106 are formed onto the layer 104, thus laminating a laser. The guide layer 103 and the active layer 104 in the structure fill the roles of light emission in the active layer 104 and the leading out of light to the guide layer 103, thus absorbing light except a recessed section by a substrate, then guiding and emitting only light oozing out to the guide layer 108. Consequently, light is confined to the section 108, and currents are injected from a region 107 held by N-GaAs 106, thus efficiently supplying the recessed section with currents. Accordingly, luminous efficiency is improved, and homogeneous output can be extracted with excellent reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed.

[Prior art]

Conventionally, when designing an optical scanning device using a plurality of semiconductor lasers or light emitting diodes (LEDs), as disclosed in Japanese Patent Application Laid-Open No. 59-126, light is emitted from a light emitter as shown in FIG. The emission direction is one point P.

The light sources were designed such that the light sources intersected at the same angle, and the scanning spot (not shown) could be scanned with a plurality of scanning spots while maintaining a good image formation state.

FIG. 3 shows a typical conventional example, and is a diagram of the optical system between the light source and the deflector, viewed from a direction perpendicular to the deflection scanning plane. 31a and 31b are semiconductor lasers, and each laser is arranged on the mount 32 so that its light beam generating surface is parallel to the end surface of the mount 32. The end faces 32a and 32b of the mount 32 on which the semiconductor lasers 31a and 31b are provided are points P where the central lights Jha and hb of the divergent light beams from the respective lasers 31a and 31b are the same.

It is set as if it had passed through.

In other words, if normal lines are drawn to the end faces 32a and 32b at the positions where the semiconductor lasers (31a, 31b) are provided, each normal line is P. The end faces 32a and 3
2b is set. Furthermore, when viewed from a direction parallel to the deflection scanning plane, the central rays ha and hb of each semiconductor laser
The position of the semiconductor laser provided on the mount 32 is set so that the position passing through 20 points is slightly displaced in a direction perpendicular to the deflection scanning plane. Above P. The point P in a predetermined vicinity of the deflection reflection surface 33 of the deflector is maintained in an optically conjugate relationship by the imaging lens 34.

In this way, in order to arrange multiple semiconductor light emitting devices (for example, semiconductor lasers) so that their respective light emission directions are different, they must be aligned on the mount and configured into a hybrid structure, as shown in the example above. I needed to. For convenience, the term "array laser" will be used below to refer to a plurality of semiconductor light emitting elements, but in principle it also applies to light emitters such as LED arrays.

Furthermore, when using a monolithically formed array laser, it is necessary to install some kind of optical system in front of the array laser. In an example disclosed in Japanese Patent Laid-Open No. 58-211735, a prism is placed in front of an array laser. This is shown in FIG.

FIG. 4 shows a cross section of a prism when a semiconductor array laser has five light emitting parts. 41 is five light emitting parts (41a, 41b, 41c, 41d, 41
42 is a prism. The central ray ha of the luminous flux from the light emitting part 41a is refracted by the inclined surface 42a, and the central ray ha of the luminous flux is refracted as if by P. It is bent as if it had passed through. Same (central ray h from 41b
b is caused by the inclined surface 42b, the central ray hd from 41d is caused by the inclined surface 42d, and the central ray he from 41e is caused by the inclined surface 42e, as if P.

It is bent as if it had passed through. Note that the central ray hc from 41c passes through the plane 42c perpendicularly, and P is on the extension line of this central ray hc. exists.

In this way, an inclined plane with a defined angle of inclination is provided corresponding to each light emitting part, and the direction of the central ray of each luminous flux after exiting the prism 42 is controlled as if it were exiting from Po. . As described above, this Po is kept conjugate with a desired position P (not shown) near the deflection/reflection surface via the optical system. Problems in this case include the precision and method of microfabrication of the prism 42, the alignment and bonding method between the prism 42 and the array laser 41, and the smaller the pitch of the array laser, the more difficult it becomes. In fact, it is almost impossible if the thickness is less than 100 μm.

On the other hand, FIG. 5 shows an attempt to have a similar effect with an optical system, that is, a relay optical system 53, with array lasers 51a, 5
This is an example in which a relay optical system 53 is interposed between a collimator lens 52 and a cylindrical lens 55 that collimate and image the light emitted from 1b, and an image is formed on a polygon surface 54, and the image is scanned in a good image formation state. The image is formed on a surface (not shown). The problem in this case is the optical path length, and the relay system itself becomes about 20 cm longer.

On the other hand, in order to solve the above-mentioned problems, the present applicant has proposed a method in which a plurality of semiconductor lasers are monolithically formed, and each semiconductor laser A semiconductor device has already been proposed in which the directions of emission are different.

[Summary of the invention]

An object of the present invention is to provide a semiconductor laser device that can be easily manufactured and that can be combined with lenses etc. to construct an optical system with a short optical path length. This will further improve the

A semiconductor laser device according to the present invention is a semiconductor device in which a plurality of semiconductor lasers are monolithically formed.
A feature of the above-described semiconductor laser is that the respective directions of light emission are different when the light is emitted from the respective resonant surfaces of the semiconductor laser.

In addition, the expression "the directions of light emitted from each laser are different" used in the following description does not mean that there is no set of lasers that emit light in the same direction (in a broad sense, it means that there are no sets of lasers that emit light in different directions). This means that there is one or more pairs.

The problem with integrating a large number of semiconductor lasers at high density is that the emission efficiency decreases due to the heat generated by carrier injection for oscillation and temperature rise, and it is no longer possible to obtain a constant optical output with a constant injection current. It disappears. This is serious when a semiconductor laser is used as a light source in an optical recording device, leading to recording errors and deterioration of recording quality.

In order to prevent the above-mentioned reduction in luminous efficiency, the specific solution proposed in the present invention is such that each semiconductor laser has a first semiconductor layer, which becomes an active layer, with a forbidden band distance from the first semiconductor layer. a fourth semiconductor layer sandwiched between second and third semiconductor layers having a large refractive index and a small refractive index, and having a forbidden band interval between the first semiconductor layer and the second and third semiconductor layers; Fourth
A fourth semiconductor layer is formed adjacent to at least one surface of the active layer, but the thickness of the fourth semiconductor layer in a portion corresponding to the current injection region is made thicker than the fourth layer thickness of the current injection region to form a refractive index distribution. This is achieved by improving the light emitting characteristics. That is, by adopting the above structure as described in the examples below, (1) the injection current required for light emission is reduced, and the amount of heat generated to obtain the same level of light output is reduced (and the operating temperature is lowered). .

(2) Good temperature characteristics, with little fluctuation in light output even during high-temperature operation.

(3) There is little variation in performance between adjacent elements, and homogeneous output can be obtained from a plurality of output ends.

(4) By providing a waveguide layer, it was possible to reduce the optical density at the output end face, prevent end face destruction, and realize a high-output laser.

Due to the above-mentioned combined effects, good light emission characteristics can be obtained regardless of the light emission history in the obliquely emitting array laser that is highly integrated as in the present invention.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 11 to 15 indicate individual semiconductor lasers, and Lla to 15a correspond to current injection regions, that is, light emission regions in each of the semiconductor lasers 11 to 15. The angles formed by the extension lines (hereinafter referred to as resonance directions) 11b to 15b of the injection regions 11a to 15a and the normal line 18 to the resonance surfaces 16 and 17 are φa, φb, φC9φd, and φe, respectively. It is formed like this.

Note that the resonant planes 16 and 17 are parallel because the cleavage planes of a crystal (e.g., GaAs) used as a substrate are normally used, but in cases where there is a possibility that the degree of parallelism will be slightly impaired, such as during dry etching. In this case, the resonance surface 16 on the laser emission front side is considered as a reference.

When the light resonated at the resonant surfaces 16 and 17 is emitted from the resonant surface 16 as a laser beam, it is bent according to Snell's law. In the figure, llc to 15c indicate the light emission direction.

Here, if the angle between an arbitrary light emission direction and the normal line 18, that is, the emission angle, is θ, then n/n. ==sinθ/si
The relationship nφ holds true. For example, considering the case where the light is emitted from a GaAs crystal, n (the refractive index of the crystal) is approximately 3.5, and n
Since o (the refractive index of air) is about 1, if φ is chosen to be 1 degree, the laser beam will be emitted at an angle of about 3.degree. and 5.degree. with respect to the normal 18.

In the embodiment shown in FIG. 1, φa, φb, φC1φd, φ
e respectively +1.0 degree, +0.5 degree, 0.0 degree,
By setting -0.5 degrees and -1.0 degrees, the output angles θa, θb, θC9θd, and θe are each +3
．． 5 degrees, +1.75 degrees, 0 sword degrees, -1.75 degrees,
We were able to create an array laser with an angle of -3.5 degrees.

FIG. 6 is a sectional view taken along line A-A' in FIG. 1.

The manufacturing process will be described in detail below using this figure.

This embodiment is shown in FIG. 101 is a substrate made of n-GaAs. On top of this, 102 n-kRo,
45 Ga O and 55 As are formed. The thickness of 109 is approximately 0.9 μm. Next, the guide layer of 103, n
=A E 0.31 Ga 0.69 The film thickness of 108 formed from As is about 0.4 μm. Further, an active layer 104 is formed thereon to a thickness of 0.08 to 0.1 μm. 0.09 ca O,9+
It is As. Furthermore, 105 (7) p A
I 0.45 Ga O, 55 As is formed to a thickness of 1.5 μm, and finally 10 6 n-GaAs is formed to a thickness of 1 to 2 μm, and a laser is laminated. The role of the guide layer 103 and the active layer 104 in this structure is that the active layer 104 emits light and guides it to the guide layer 103. At this time, light other than the concave portions is absorbed by the substrate, and only the light leaking into the guide layer 10B is guided and emitted. In this way, the light is 1
Trapped in part 08.

In order to further increase efficiency, current confinement is formed. 107 is a region in which Zn is diffused. By injecting the current from the region 107 sandwiched between the n-GaAs layers 106, the current is efficiently supplied to the recess. Thereby, laser oscillation can be performed more efficiently. 110 and 111 indicate p-type and n-type electrodes. 110 is Au
-Zn/Au, and 111 is Au-G e -N i
/ A u.

The advantage of directing the light to the guide layer 103 is that the output of edge destruction is improved. This configuration is suitable for high power operation. Further, this guide layer may be formed on top of the active layer. The guide layer needs to be sandwiched between two layers having a larger band gap and a smaller refractive index than the guide layer. In the present invention, the laser is formed using an n-GaAs substrate, but the laser may also be formed using p-GaAs. At that time, it is sufficient to invert the P/N of the present invention.

In the semiconductor device according to the present invention, array lasers with different light emission directions are created using cleavage planes, but the present invention is not limited to array lasers using cleavage planes. Depending on mounting considerations, it is also possible to employ, for example, a resonant surface formed by a wet process or a dry process on one side or both sides. Examples are shown in Figures 2-1 and 2-2.

213a to 213e, 223a in each figure
223c is an injection region, each having an independent injection electrode. 214a to 2L4e, 215a
~215e (b.

(c, d not shown) are the resonator surfaces formed by etching. Also, in Figure 2-2, 224a
.

224b, 224c, 225a, 225b, and 225c are resonator surfaces formed by etching.

It should be noted that the first semiconductor layer, which is the active layer shown in the claims, and the second semiconductor layer sandwiching the first semiconductor layer are the active layers. In the third semiconductor layer structure, the second. The third region includes a superlattice structure that is not an active layer and a semiconductor layer whose composition is continuously changed;
A generation layer is a region where carrier recombination occurs and a region of several thousand Å formed adjacent to the region where carrier recombination occurs.
It also contains a thin layer of: For example, single quantum wells (and multiple quantum wells, and ordinary eyebrows of about 0.1 μm)
It includes a barrier layer of several to several thousand layers formed on both sides of the light, and a thin layer of 0.1 μm or less that causes light confinement.

〔Effect of the invention〕

As explained above, the present invention has made it possible to extract homogeneous output with high luminous efficiency and high reproducibility from different emission directions in a conventional semiconductor laser device. Furthermore, since the light emitting direction from each laser is different, laser beams from multiple points can be imaged well on the medium using a scanning optical system, making it suitable as a light source for optical devices such as laser beam printers. Extremely advantageous.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of a semiconductor device according to the present invention, FIGS. 2-1 and 2-2 are plan views showing modified examples of the present invention, and FIG. 3 is a plan view showing a semiconductor device according to an embodiment of the present invention. Figure 4 shows a conventional example in which an array laser with a constant output direction and a prism are combined to have different output directions, and Figure 5 shows an attempt to correct an array laser with a constant output direction using an optical system. FIG. 6 is a schematic cross-sectional view showing a configuration example of a semiconductor laser. 11-15... Semiconductor laser, 16.17... Resonance surface.

Claims (1)

[Claims] (1) A plurality of semiconductor lasers are formed monolithically, and each semiconductor laser has a first semiconductor layer serving as an active layer that has a larger forbidden band interval and a smaller refractive index than the first semiconductor layer. A fourth semiconductor layer is sandwiched between the second and third semiconductor layers and has a forbidden band interval between the first semiconductor layer and the second and third semiconductor layers, and the fourth semiconductor layer is an active layer. A fourth semiconductor layer is formed adjacent to at least one surface of the semiconductor layer, but the thickness of the fourth semiconductor layer in the portion corresponding to the current injection region is made thicker than the fourth layer thickness of the pond, and a refractive index distribution is formed to form a stripe shape. 1. A semiconductor laser device configured to confine light, wherein the angle between the direction of the stripe and the resonant surface is varied depending on the semiconductor laser, and a plurality of lights are emitted in different directions.